Carson D. Slabaugh

The development of an optically accessible, high-power combustion test rig.

This work summarizes the development of a gas turbine combustion experiment which will allow advanced optical measurements to be made at realistic engine conditions. Facility requirements are addressed, including instrumentation and control needs for remote operation when working with high energy flows. The methodology employed in the design of the optically accessible combustion chamber is elucidated, including window considerations and thermal management of the experimental hardware under extremely high heat loads. Experimental uncertainties are also quantified. The stable operation of the experiment is validated using multiple techniques and the boundary conditions are verified. The successful prediction of operating conditions by the design analysis is documented and preliminary data are shown to demonstrate the capability of the experiment to produce high-fidelity datasets for advanced combustion research.

Effect of Aviation Fuel Type and Fuel Injection Conditions on Non-reacting Spray Characteristics of a Hybrid Airblast Fuel Injector

I njector spray characteristics have a significant influence on the combustion performance in a gas turbine engine, including an impact on dynamics, emissions and component life. Furthermore, commercial aviation faces fuel cost, environmental, and energy security challenges that arise from the use of petroleum based jet fuels. Sustainable alternative jet fuels can help address these challenges and need to be characterized in their spray performance. The present work describes the detailed characterization of several alternative fuels using a hybrid airblast atomizer on the basis of spray shape, droplet size and velocity distribution at a range of operating conditions including fuel temperature, injector pressure drop and spray chamber pressure and temperature. The characterization is done using optical patternation, phase Doppler anemometry (dual-PDPA) and high speed back-lit imaging. The measurements obtained as part of this work provide the validation data-set for computational modeling of the spray behavior which forms a critical part of the broader project. The results show a strong influence of the fuel temperature on the spray, with lower temperature (290 K to 240 K) decreasing the atomization quality by 14%, while the effect of fuel injection pressure on the spray is minimal. A large effect of pressure drop across the injector is seen on the spray, with a change from 2% to 6% leading to a decrease in drop size of up to 36%, which can result of a shift in the secondary breakup regime of the spray.

Heat Transfer in a Rectangular Channel with Dimples Applied to One Wall

Nusselt number augmentation, and overall friction augmentation throughout the length of the duct. The largedimple feature was found to promote significant intensification of convective heat transfer (as high as 80%) at a Reynolds number of 30,000. Furthermore, the double-dimple surface feature was found to promote heat transfer augmentation comparable with the large-dimple feature, accompanied by the pressure loss penalty of the modest small dimple. By contributing to a clearer understanding of the effects produced by these geometries, the development of more effective channel-cooling designs can be achieved.

The Application of Stereoscopic PIV in a Liquid-Fueled Gas Turbine Combustor

Pratt, Andrew Charles MSAA, Purdue University, December 2015. The application of Stereoscopic PIV in a Liquid-fueled Gas Turbine Combustor. Major Professor: Robert P. Lucht, School of Mechanical Engineering. Strict regulations on aviation gas turbine engine emissions and fuel consumption have driven the development of new lean burning, efficient gas turbine injectors. In an effort to increase fundamental understanding and support modeling efforts, great advancements have taken place in experimental measurement techniques. Specifically, in the field of laser diagnostics. This work describes the application of high repetition rate stereoscopic particle image velocimetry to a gas turbine combustor operating at representative engine conditions. A motivation and brief background of this research is provided. An introduction to Stereoscopic Particle Image Velocimetry (SPIV) and its development is included with a description of the experimental systems and the challenges associated with acquiring useful data in high pressure and high thermal power. The facility capabilities and test stand capabilities are presented along with the operational configuration for both the experimental and diagnostic systems. Finally, results are presented from two operating conditions, one with combustion and one without. Both 3-component SPIV and 2-component PIV data were collected simultaneously at 6 kHz. The vector fields generated from both techniques are compared both qualitatively and quantitatively.

PIV Study on the Dimple Mid-Plane of a Narrow Rectangular Channel With Dimples Applied to One Wall

This paper presents an investigation of the fluid flow in the fully developed portion of a rectangular channel (Aspect Ratio of 2) with dimples applied to one wall at channel Reynolds numbers of 20,000, 30,000, and 40,000. The dimples are applied in a staggered-row, racetrack configuration. Results for three different dimple geometries are presented: a large dimple, small dimple, and double dimple. Heat transfer and aerodynamic results from preceding works are presented in Nusselt number and friction factor augmentation plots as determined experimentally. Using particle image velocimetry, the region near the dimple feature is studied in detail in the location of the entrainment and ejection of vortical packets into and out of the dimple; the downstream wake region behind each dimple is also studied to examine the effects of the local flow phenomenon that result in improved heat transfer in the areas of the channel wall not occupied by a feature. The focus of the paper is to examine the secondary flows in these dimpled channels in order to support the previously presented heat transfer trends. The flow visualization is also intended to improve the understanding of the flow disturbances in a dimpled channel; a better understanding of these effects would lead the development of more effective channel cooling designs. Copyright © 2011 by ASME.

Gas Turbine Fuel System and Combustion Study with High Temperature Fuel Injection

Combustion experiments have been conducted to assess the influence of fuel temperature on emissions and performance using a Rolls-Royce 501K combustor as a platform for the study. A total of 27 tests were conducted using (Jet-A) fuel at room temperature, 250 °F, and 450 °F target fuel temperatures. Fuel was sparged to remove dissolved oxygen content for the high temperature tests; typical oxygen levels in the fuel at the delivery point to the test article were 0.2% of fully saturated values. Unburned hydrocarbon, carbon monoxide and NOx emissions were recorded for all conditions and high frequency pressure measurements were included in the combustor along with conventional pressure and temperature instrumentation. Combustor operation with heated fuel seems to generate measurable changes in combustion efficiency and noise content. Additionally, these phenomena seem to relate to variations in the operational envelope of the combustor.

A Study of Heat Transfer Augmentation in a Rectangular Channel with Dimples Applied to One Wall

This study is an investigation of the heat transfer augmentation through the fullydeveloped portion of a narrow rectangular duct (AR=2) characterized by the application of dimples to the bottom wall of the channel. The geometries are studied at channel Reynolds numbers of 20000, 30000, and 40000. The purpose is to understand the contribution of dimple geometries in the formation of flow structures that improve the advection of heat away from the channel walls. Experimental data reported includes the local and Nusselt number augmentation of the channel walls and the overall friction augmentation throughout the length of the duct. The large dimple feature was found to promote significant intensification of convective heat transfer, as high as eighty percent, at a Reynolds number of 30000. Furthermore, the double dimple surface feature was found to promote heat transfer augmentation comparable to the large dimple feature, accompanied by the pressure loss penalty of the modest small dimple. By contributing to a clearer understanding of the effects produced by these geometries, the development of more effective channel-cooling designs can be achieved.

Heat Transfer and Friction Augmentation in High Aspect Ratio, Ribbed Channels With Dissimilar Inlet Conditions

This work is an investigation of the heat transfer and pressure-loss characteristics in a rectangular channel with ribs oriented perpendicular to the flow. The novelty of this study lies in the immoderate parameters of the channel geometry and transport enhancing features. Specifically, the aspect ratio (AR) of the rectangular channel is considerably high, varying from 15 to 30 for the cases reported. Also varied is the rib-pitch to rib-height (p/e), studied at two values, 18.8 and 37.3. Rib-pitch to rib-width (p/w) is held to a value of two for all configurations. Channel Reynolds number is varied between approximately 3000 and 27,000 for four different tests of each channel configuration. Each channel configuration is studied with two different inlet conditions. The baseline condition consists of a long entrance section leading to the entrance of the channel to provide a hydrodynamically developed flow at the inlet. The second inlet condition studied consists of a cross-flow supply in a direction perpendicular to the channel axis, oriented in the direction of the channel width (the longer channel dimension). In the second case, the flow rate of the cross-flow supply is varied to understand the effects of a varying momentum flux ratio on the heat transfer and pressure-loss characteristics of the channel. Numerical simulations revealed a strong dependence of the local flow physics on the momentum flux ratio. The turning effect of the flow entering the channel from the cross-flow channel is strongly affected by the pressure gradient across the channel. Strong pressure fields have the ability to propagate farther into the cross-flow channel to “pull” the flow, partially redirecting it before entering the channel and reducing the impingement effect of the flow on the back wall of the channel. Experimental results show a maximum value of Nusselt number augmentation to be found in the 30:1 AR channel with the aggressive augmenter (p/e = 37.3) and a high momentum flux ratio: Nu/Nuo = 3.15. This design also yielded the friction with f/f0 = 2.6.

HEAT TRANSFER AND FRICTION IN HIGH ASPECT RATIO INTERNAL COOLING CHANNELS MACHINED WITH VARIOUS TECHNIQUES

This work is an investigation of the heat transfer and pressure loss characteristics of three channels each manufactured with a different machining process. The first channel is machined from a wheel cutter and the last two channels are machined from a waterjet. Each channel configuration is tested at various channel flowrates; channel Reynolds number is varied between approximately 3,000 and 27,000. The channels are also tested under two different flow inlet conditions, a hydrodynamically fully developed inlet condition and a cross-flow inlet condition, cross-flow Reynolds numbers is also varied between 150,000 and 300,000. The Nusselt number augmentation and friction factor augmentation of each channel are reported.

Heat Transfer and Friction Augmentation in a Narrow Rectangular Duct with Ribs Applied to One Wall

This paper is an investigation of the heat transfer augmentation in the fully-developed portion of a narrow rectangular duct (AR=2) with rib geometries applied to the bottom wall. Testing is performed at Reynolds numbers of 20000, 30000, and 40000. Thermal efficiency of the channel is the ultimate goal for any cooling channel design. The purpose of the paper is to find the performance of varying rib size on the heat transfer and friction performance of the channel. Data reported includes the Nusselt Number Augmentation of the side walls of the channel and the thermal performance of the entire duct. The higher blockage of the larger feature contributes to a high Nusselt Number Augmentation value, but also to a higher friction factor augmentation; both of these values determine the thermal performance in the channel. A better understanding of the effects produced by these geometries will help in the design and development of more effective cooling-channel design.